Dual-Cross-Linked Nanocellulose Films with Multifunctional and Enhanced Barrier Properties for Food Preservation

Nanocellulose holds immense potential for designing sustainable food packaging materials owing to its outstanding film-forming properties and renewability. However, its inherent water sensitivity and lack of biological activity limit its practical applications. Here, we report the use of a synergistic dual-cross-linking strategy involving polyamide-epichlorohydrin (PAE) and tannic acid (TA) to engineer high-performance TEMPO-oxidized cellulose nanofiber (TOCNF) based films. Specifically, a robust physical framework was constructed through covalent cross-linking between PAE and TOCNF. Simultaneously, the polyphenolic hydroxyl groups of TA formed a network of multiple hydrogen bonds, inducing structural shrinkage during the thermosetting film’s formation process, thereby significantly achieving film densification. Benefiting from this unique structure, the optimized PAE/TA dual-cross-linked TOCNF films achieved an outstanding tensile strength of 72.45 MPa and a remarkable wet tensile strength of 5.95 MPa, representing increases of 74.3% and 344.0% over the neat TOCNF film, respectively. Furthermore, the dual-cross-linking strategy significantly improved the film’s barrier properties, reducing the water vapor permeability (WVP) by 88.8% to 0.86 × 10–10 g/(m·s·Pa) and the oxygen transmission rate (OTR) by 63.6% to 23.18 cm3/(m2·24 h·0.1 MPa). In addition, the film exhibits excellent UV resistance, antioxidant properties, and antimicrobial activity. Finally, PAE/TA dual-cross-linked TOCNF films also demonstrated excellent practical preservative and freshness-retention performance in experiments involving fresh pork. This synergistic cross-linking strategy guides the development of multifunctional, sustainable bio-based packaging materials to replace traditional nonbiodegradable plastics.